The field of the invention relates to techniques for the detection and identification of an analytes, and in a specific embodiment, electronic olfaction.
Human beings have five classical sensesxe2x80x94sight, smell, taste, hearing, and touch. Since the earliest times, humankind has sought techniques and devices for enhancing and extending these senses. Many of the devices and instruments that have been developed to extend human perception are considered among of the most revolutionary inventions in history. These inventions have had a profound impact on human civilization and have led to many additional breakthroughs and discoveries. Just a few of the many instruments developed to extend the reach of human perception include the telescope, microscope, stethoscope, X-rays, radio, audio amplifier, scanning electron microscope, night-vision goggles, and many others.
As can be expected, there has been considerable interest in developing a device or instrument for the general detection of analytes in a fluid, vacuum, air, or other medium. A specific instance of an analyte detector is a device for sensing smell or odors (i.e., analytes in air). It is well recognized that some animals like dogs have a keener sense of smell than human beings. Because of their xe2x80x9cnoses,xe2x80x9d dogs have been utilized for many tasks including, for example, the detection of bombs, mines, drugs, poison gases, and illegal contraband; dogs also aid in the search and rescue of humans. Devices for sensing smell would be useful for the traditional applications where animals are used, as well as for a multitude of uses where animals are impractical or inappropriate.
Moreover, a device for the general detection of analytes has potentially many more applications than a specific device for detecting smells. For example, the uses for a device for analyte detection include the detection of chemical leaks, quality control in food processing, medical diagnosis and testing, fabrication and manufacture of commercial and industrial goods, pharmaceutical production, testing or evaluating any odorant or analyte in any medium (e.g., fuel, oil, wine, solvents), and many other applications. An instrument for analyte detection would be highly desirable in industries and applications such as the chemical and petrochemical sectors, food, fragrance, medical, automotive, military, environmental, health and safety, and indoor air quality.
Therefore, it is desirable to develop techniques and devices for the detection of analytes. An approach for sensing smells is to use surface acoustic wave (SAW) resonators. However, the signal transduction mechanism for SAW devices has many shortcoming because these devices utilize relatively complicated electronics, which are somewhat costly. Furthermore, SAW devices are generally extremely sensitive to both mass and acoustic impedance changes, and may not be suitable for use in all environments.
Therefore, there is a need for techniques and systems for analyte detection, especially ones that are relatively low cost, easy to manufacture, provide rapid response, and produce accurate differentiation between different analytes and different concentrations of the same analyte.
The present invention provides techniques and a system for detecting and identifying analytes in fluids. Techniques for fabricating and manufacturing sensors to detect analytes are also provided. Analytes may include smells, tastes, vapors, odors, gases, fluids, liquids, and chemicals, among others. The analyte may be in air, fluid, or other medium. In the present invention, an analyte is sensed by sensors that output electrical signals in response to the analyte. The electrical signals may be preprocessed by filtering and amplification. This preprocessing may also include adapting the sensor and electronics to the environment in which the analyte exists. The electrical signals may be further processed to classify and identify the analyte.
In a specific embodiment, the present invention is used to implement an electronic olfaction system or xe2x80x9csynthetic nose.xe2x80x9d This system will perform an analogous function as a mammalian olfactory system, although the electronic system will have additional capabilities. Such an electronic nose system will reveal the identification and concentration of vapors. Another embodiment for the analyte detection system of the present invention is used to implement a device for tasting. This device would function similarly to a mammalian tongue. There are many other possible specific applications of the techniques of the present invention, too numerous to name here.
Sensors of the present invention are fabricated on a substrate or other suitable material. For example, in one embodiment, the sensors are formed using semiconductor processing techniques on a single integrated circuit. The integrated circuit or chip contains a plurality of sensors, each contained at a sensor site. The sensor sites may be arranged in rows and columns. Structures or other means are constructed on the substrate to constrain a sensor material at each sensor site. For example, the sensor sites may be a plurality of sensor wells that will hold the sensor material.
The sensor material applied to or formed at one sensor site may have a different composition from the sensor material at a different site. For example, each sensor in the analyte detection system may have a different composition from every other sensor. The sensor material may be a mixture of a nonconductive material and a conductive material such as carbon black; the composition or concentration of carbon black will vary for each sensor on the chip. By providing a system of diverse sensors, each sensor may have a different response characteristic for a given analyte. The sensor""s response to an analyte can be characterized by a measurable change in an electrical property such as resistance, capacitance, or inductance.
There is also an electrical connection at each sensor site to route the electrical signals from the sensor material to other circuitry for further processing. The circuitry may be on-chip with the sensors, or may be off-chip, such as on a different integrated circuit. The data from the sensors may be processed using a computer. In a specific embodiment, the circuitry for each sensor site is formed beneath or interspersed with the sensor sites on the integrated circuit.
The electrical signals from the sensors are further processed to classify the response to the analyte. The processing electronics may include electronic circuits to amplify and enhance the received data from the sensors. Each analyte may have a particular xe2x80x9cfingerprint.xe2x80x9d The analyte will be identified based on this fingerprint. The signal processing for the identification and classification of the analyte is performed by on-chip or off-chip electronic circuitry. For example, classification is performed using a neural network, among other techniques. Therefore, using the techniques and system of the present invention, an analyte can be distinguished and identified.
An aspect of the present invention is the use of a number of sensors to detect analytes. A further aspect of the present invention is the use of an integrated circuit having an array of sensors to detect analytes. A still further aspect of the present invention is the use of a semiconductor process to fabricate an integrated circuit having an array of sensors used to identify an analyte. The present invention includes the use of electronic circuitry to process the electrical signals from a plurality of analyte sensors to identify an analyte, where each sensor includes a mixture of nonconductive organic material and a conductive material.
In a specific embodiment, the present invention is an integrated circuit including a plurality of sensor sites formed on a substrate, each sensor site for constraining the sensor material. The integrated circuit further includes an electrical terminal formed to measure an electrical property of the sensor material. The electrical property is an impedance, resistance, capacitance, inductance, or other electrical property. The sensor material may be a mixture of a nonconductive organic material and a conductive material.
In a further embodiment, the present invention includes receiving data from a number of sensors for detecting chemical analytes, where each sensor has a first and second output terminal. There are plurality of electronic circuits, coupled to receive the electrical data from the first and second output terminals of the sensor. This electrical data may be an analog weight. The electrical circuitry may include a floating gate device such as a Flash or EEPROM cell to store the analog weight. The electrical data (e.g., analog weights) is further used to identify the analyte. The identification scheme may include use of a neural network.